The present invention relates generally to brake lathes and particularly to a brake lathe that can finish the wear surface of both brake disks and brake drums of vehicular breaking systems. More specifically, the present invention is directed to a unique hand wheel engagement/disengagement mechanism for the drive selection operation of a brake lathe machine that employs a single slide drive motor to drive the lead screw for a lateral cut (to finish the surface of the rotor of a disk brake system) or for an in-line cut (to finish the surface of the drum of a drum type brake system). With this particular mechanism, the hand wheel can be moved between an "in" position and an "out" position to select the configuration of the brake lathe for finishing a rotor or a drum, and once positioned, the hand wheel can be manually rotated to adjust the location of the tool bit on a rotor, or the depth of cut of the bit on a drum, that is to be turned on the machine. The mechanism is efficient, simple, has few pans to wear or break, is relatively inexpensive to manufacture, and is easy to operate.
It will be appreciated by those skilled in the art that braking systems for cars, trucks, buses, and the like (all referred to herein generally as "vehicles"), are subject to tremendous heat and pressure, and in the life of a vehicular braking system, pads are activated against drums and rotors thousands if not millions of times. In the design of vehicles, it is a design objective to reduce weight, particularly in functional items such as braking systems, which means that size and material specifications are constantly decreasing the thickness, weight and strength of vehicular braking parts. With these designs, brake system rotors become worn over time to form grooves in the wear surface which results in a loss of braking capacity. Other wear problems include "run-out" ("run-out" describing intermittent wear on a rotor about its perimeter) which causes brake pulsation; or the system may experience rotor warp which is a warp or bending of the rotor so that the rotor is not planer in shape, thus causing an uneven contact by the brake pads on the rotor. Rotor warp impairs the ability of the pads to apply consistent pressure to the rotor, thereby generating heat and ultimately leading to further destruction of the braking system.
In drum type systems, the drum is subject to pressures which may cause it to wear slightly out of round and become egg shaped, thereby reducing the effectiveness of the pressure of the pads against the drum. Uneven cross sectional wear of the pad on the drum can cause the face of the drum to become tapered or bell-mouthed, the consequence of either variety of uneven wear resulting in a poor contact between the brake pad and the drum and thereby generating greater heat and ultimately the destruction of the pads. These problems cause the braking system to become less and less effective until it deteriorates and has to be replaced completely.
All of these problems are well known in the art and are generally addressed by a resurfacing of the rotors and drums of braking systems through a process which is referred to in the industry as "turning". Turning the rotor of a disk brake system or the drum of a drum brake system is a reference to a refinishing of the wear surface of the element so that, with respect to a rotor, the surface is in a substantially perfect plane about the outer perimeter of the rotor, and with respect to a brake drum, the wear surface is round and flat to mate perfectly with the shoes which force the brake pad against the drum.
Brake lathes have been available for many years to turn brake rotors and brake drums. However, Applicant has recognized the need for improvement of existing brake lathes. Brake lathes currently available on the market are large, cumbersome to operate and have many working parts that are subject themselves to wear, destruction and need for replacement. Further, existing brake lathes require multiple motors to drive the lead screws with one motor for driving the lead screw for a lateral cut and a second motor for driving a lead screw to make an inline cut.
What is needed then is a brake lathe machine that is relatively simple to manufacture and assemble; that has fewer working parts; that is sturdy and structurally stable through repeated uses with a minimum of size and bulk; that can form both inline and lateral cuts using a single drive motor selectively to drive lead screws in perpendicular directions, depending on the configuration of the system, to propel the cutting edge in the desired direction; and that is compact, efficient, and easy to operate. Such a machine should also have a hand wheel engagement/disengagement mechanism for the drive selection operation of the machine that the operator can move between multiple positions to select the configuration of the lathe for finishing a rotor or a drum, and include a structure so that once positioned, the hand wheel can be manually rotated to adjust the location of the tool bit on a rotor, or the depth of cut of the bit on a drum, that is to be turned on the machine.